In many instances it is desirable to actuate apparatus on a vehicle when the velocity of the vehicle reaches a predetermined value. If the vehicle is traveling through a fluid, such as air or water, the velocity of the fluid passed the surfaces of the vehicle may provide an indication of the velocity of the vehicle. If the velocity of the vehicle is high relative to the velocity of any disturbances in the fluid, the velocity of the fluid passed the surfaces of the vehicle is generally proportional to the velocity of the vehicle.
In the prior art, pitot tubes are used to provide an indication of the velocity of the fluid flowing past the vehicle and hoses are attached to the pitot tube and to a diaphragm activated switch. However, diaphragm actuated switches are relatively complicated to manufacture and are prone to receive dirt, bugs and the like therein which reduce the reliability thereof.